The bpf_set_retval() helper is used by cgroup BPF programs to set the
return value of the target hook. The argument type for this helper is
ARG_ANYTHING. This allows setting a positive value, which no cgroup
hook expects and can cause issues, such as:
- BPF_LSM_CGROUP: a positive value from bpf_lsm_socket_create bypasses
the err < 0 check in __sock_create(), leaving the socket object
unallocated. The positive return value is then propagated to the
syscall entry __sys_socket(), which also bypasses the IS_ERR() guard
and ultimately causes a NULL pointer dereference.
- BPF_CGROUP_DEVICE: a positive value can be returned through cgroup
device bpf prog -> devcgroup_check_permission() -> bdev_permission()
-> bdev_file_open_by_dev(), where ERR_PTR(positive) produces a pointer
that IS_ERR() does not catch, leading to a wild pointer dereference.
- BPF_CGROUP_SOCK: a positive value can be returned through cgroup sock
bpf prog -> __cgroup_bpf_run_filter_sk() -> inet_create() ->
__sock_create(), where inet_create() frees the newly allocated sk
via sk_common_release() and sets sock->sk = NULL on the non-zero
return, but __sock_create() only checks err < 0 for cleanup, so a
positive retval bypasses cleanup and returns a socket with NULL sk
to userspace, triggering a NULL pointer dereference on subsequent
socket operations.
- BPF_CGROUP_SYSCTL: a positive value can be returned through the cgroup
bpf prog -> __cgroup_bpf_run_filter_sysctl() -> proc_sys_call_handler(),
where a non-zero return bypasses the normal sysctl proc_handler and is
returned directly to userspace as return value of read() or write()
syscall.
So add validation for the argument of the bpf_set_retval() helper.
For BPF_LSM_CGROUP, enforce the LSM hook specific range returned by
bpf_lsm_get_retval_range().
For all other cgroup program types, restrict the argument to
[-MAX_ERRNO, 0], which matches the kernel convention of 0 for success
and negative errno for error.
BPF_CGROUP_GETSOCKOPT is an exception, since valid getsockopt
implementations may return positive values, as allowed by commit
c4dcfdd406 ("bpf: Move getsockopt retval to struct bpf_cg_run_ctx").
Also refine the return value range of bpf_get_retval() so that
values returned by bpf_get_retval() can be passed directly to
bpf_set_retval() without extra manual bounds checking.
Fixes: b44123b4a3 ("bpf: Add cgroup helpers bpf_{get,set}_retval to get/set syscall return value")
Fixes: 69fd337a97 ("bpf: per-cgroup lsm flavor")
Reported-by: Quan Sun <2022090917019@std.uestc.edu.cn>
Closes: https://lore.kernel.org/all/567d3206-74a5-44e5-99c6-779c425f399e@std.uestc.edu.cn
Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
Link: https://lore.kernel.org/r/20260605140243.664590-3-xukuohai@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Test sk_bypass_prot_mem passes an unchecked value as argument to helper
bpf_set_retval(). The argument can be outside the valid range enforced
by the strict retval validation added in the next patch.
Restrict the argument to -EFAULT when it is outside the valid range, so
the test will not be rejected by the verifier when retval validation
is enforced.
Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
Link: https://lore.kernel.org/r/20260605140243.664590-2-xukuohai@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Dawei Feng says:
====================
bpf: fix sysctl new-value handling in __cgroup_bpf_run_filter_sysctl
This series fixes three bugs in the sysctl write-buffer replacement path
of __cgroup_bpf_run_filter_sysctl(). It resolves a kvzalloc()/kfree()
mismatch, adds a missing NUL terminator to the replacement string, and
updates a stale return value check to safely restore the replacement
functionality.
Patch Summary:
- patch 1 NUL-terminates the replaced sysctl value
- patch 2 uses kvfree() for the replaced sysctl write buffer
- patch 3 restores sysctl new-value replacement
Changelog:
v2 -> v3:
- reordered patches 1 and 2
- added the missing Reviewed-by/Acked-by tags to patches 2 and 3
- fixed the incorrect Fixes tag in patch 3
- simplified the dynamic test logs in patch 1 and 2, and updated
titles
====================
Link: https://patch.msgid.link/20260603105317.944304-1-dawei.feng@seu.edu.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Commit 4e63acdff8 ("bpf: Introduce bpf_sysctl_{get,set}_new_value
helpers") changed the success return value to 0, but failed to update the
corresponding check in __cgroup_bpf_run_filter_sysctl(). Since
bpf_prog_run_array_cg() now returns 0 on success, the legacy ret == 1
condition is never satisfied. As a result, the modified value is ignored,
and bpf_sysctl_set_new_value() fails to replace the write buffer.
Fix this by checking for a return value of 0 instead, so cgroup/sysctl
programs can correctly replace the pending sysctl buffer.
This bug was discovered during a manual code review. Tested via a
cgroup/sysctl BPF reproducer overriding writes to a target sysctl.
Pre-fix, bpf_sysctl_set_new_value("foo") was silently ignored: the write
returned 8192 and the value remained "600". Post-fix, the BPF replacement
buffer properly propagates: the write returns 3 and the value updates to
"foo".
Fixes: f10d059661 ("bpf: Make BPF_PROG_RUN_ARRAY return -err instead of allow boolean")
Cc: stable@vger.kernel.org
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Zilin Guan <zilin@seu.edu.cn>
Signed-off-by: Dawei Feng <dawei.feng@seu.edu.cn>
Reviewed-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Acked-by: Xu Kuohai <xukuohai@huawei.com>
Link: https://lore.kernel.org/r/20260603105317.944304-4-dawei.feng@seu.edu.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
proc_sys_call_handler() allocates its temporary sysctl buffer with
kvzalloc() and passes it to __cgroup_bpf_run_filter_sysctl(). Since
kvzalloc() may fall back to vmalloc() for large allocations, freeing
that buffer with kfree() is wrong and can corrupt memory.
Use kvfree() to safely handle both kmalloc and kvzalloc()/vmalloc
allocations.
The bug was first flagged by an experimental analysis tool we are
developing for kernel memory-management bugs while analyzing
v6.13-rc1. The tool is still under development and is not yet publicly
available. Manual inspection confirms that the bug is still
present in v7.1-rc5.
Reproduced the bug based on v7.1-rc4 in a QEMU x86_64 guest booted with
KASAN and CONFIG_FAILSLAB enabled. To exercise the replacement path, the
test tree also included the accompanying fix for the stale ret == 1
check in __cgroup_bpf_run_filter_sysctl(). The reproducer confines
failslab injections to the proc_sys_call_handler() range, uses
stacktrace-depth=32, and injects fail-nth=1 while writing 8191 bytes to
/proc/sys/kernel/domainname from a task in the target cgroup. Under
that setup, fail-nth=1 triggered the fault:
BUG: unable to handle page fault for address: ffffeb0200024d48
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: Oops: 0000 SMP KASAN NOPTI
CPU: 2 UID: 0 PID: 209 Comm: repro_proc_sys_ Not tainted 7.1.0-rc4-00686-g97625979a5d4 PREEMPT(lazy)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014
RIP: 0010:kfree+0x6e/0x510
...
Call Trace:
<TASK>
? __cgroup_bpf_run_filter_sysctl+0x626/0xc30
__cgroup_bpf_run_filter_sysctl+0x74d/0xc30
? __pfx___cgroup_bpf_run_filter_sysctl+0x10/0x10
? srso_return_thunk+0x5/0x5f
? __kvmalloc_node_noprof+0x345/0x870
? proc_sys_call_handler+0x250/0x480
? srso_return_thunk+0x5/0x5f
proc_sys_call_handler+0x3a2/0x480
? __pfx_proc_sys_call_handler+0x10/0x10
? srso_return_thunk+0x5/0x5f
? selinux_file_permission+0x39f/0x500
? srso_return_thunk+0x5/0x5f
? lock_is_held_type+0x9e/0x120
vfs_write+0x98e/0x1000
...
</TASK>
With this fix applied on top of the same test setup, rerunning the
reproducer with fail-nth=1 yields no corresponding Oops reports.
Fixes: 4508943794 ("proc: use kvzalloc for our kernel buffer")
Cc: stable@vger.kernel.org
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Reviewed-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Zilin Guan <zilin@seu.edu.cn>
Signed-off-by: Dawei Feng <dawei.feng@seu.edu.cn>
Link: https://lore.kernel.org/r/20260603105317.944304-3-dawei.feng@seu.edu.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
When writing to sysctls, proc_sys_call_handler() guarantees that the
buffer passed to proc handlers is NUL-terminated. If
bpf_sysctl_set_new_value() replaces the pending sysctl value, it can
hand a replacement buffer directly to proc handlers. However, the
helper currently copies only buf_len bytes into that buffer without
appending a NUL terminator, leaving downstream parsers vulnerable to
out-of-bounds access.
Fix this by appending a '\0' after the replaced value to restore the
expected sysctl semantics. Since the helper already rejects buf_len
greater than PAGE_SIZE - 1, there is always room for the extra byte.
Reproduced in a QEMU x86_64 guest booted with KASAN while exercising
the sysctl replacement path with a cgroup/sysctl BPF program. The
reproducer targets `/proc/sys/net/core/flow_limit_cpu_bitmap`, fills
the original user write buffer with non-zero bytes, and overrides the
sysctl value so the replacement buffer lacks a terminating NUL. Under
that setup, the pre-fix kernel reported:
BUG: KASAN: slab-out-of-bounds in strnchrnul+0x72/0x90
Read of size 1 at addr ffff88800de57000 by task repro_patch3/66
CPU: 0 UID: 0 PID: 66 Comm: repro_patch3 Not tainted 7.1.0-rc3-00269-g8370ca1f87cc #6 PREEMPT(lazy)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x68/0xa0
print_report+0xcb/0x5e0
? __virt_addr_valid+0x21d/0x3f0
? strnchrnul+0x72/0x90
? strnchrnul+0x72/0x90
kasan_report+0xca/0x100
? strnchrnul+0x72/0x90
strnchrnul+0x72/0x90
bitmap_parse+0x37/0x2e0
flow_limit_cpu_sysctl+0xc6/0x840
? __pfx_flow_limit_cpu_sysctl+0x10/0x10
? __kvmalloc_node_noprof+0x5ba/0x870
proc_sys_call_handler+0x31d/0x480
? __pfx_proc_sys_call_handler+0x10/0x10
? selinux_file_permission+0x39f/0x500
? lock_is_held_type+0x9e/0x120
vfs_write+0x98e/0x1000
...
</TASK>
The buggy address is located 0 bytes to the right of
allocated 4096-byte region [ffff88800de56000, ffff88800de57000)
With this fix applied, rerunning the same sysctl-targeted path yields
no corresponding KASAN reports.
Signed-off-by: Zilin Guan <zilin@seu.edu.cn>
Signed-off-by: Dawei Feng <dawei.feng@seu.edu.cn>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20260603105317.944304-2-dawei.feng@seu.edu.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Leon Hwang says:
====================
bpf: Update transport_header when encapsulating UDP tunnel in lwt
Currently, bpf_lwt_push_ip_encap() does not update skb->transport_header.
When a driver, e.g. ice, reuses the stale skb->transport_header to
offload checksum computation to NIC hardware, VxLAN packets encapsulated
by bpf_lwt_push_encap() helper may be dropped due to incorrect checksum.
Update skb->transport_header in bpf_lwt_push_ip_encap() whenever the
encapsulated packet uses UDP, so checksum offload works correctly.
Changes:
v3 -> v4:
* Address comments from Emil:
* Make the logic of skb_set_transport_header() clearer in patch #1.
* Fold the code of fexit_lwt_push_ip_encap() into test_lwt_ip_encap.c in
patch #2.
* Resolve assorted issues of test in patch #2.
* v3: https://lore.kernel.org/bpf/20260601150203.20352-1-leon.hwang@linux.dev/
v2 -> v3:
* Drop patch #1 and #2 of v2 that aim to resolve potential issues
reported by sashiko (per Alexei).
* Check target IP version and UDP tunnel in test (per sashiko).
* v2: https://lore.kernel.org/bpf/20260529151351.69911-1-leon.hwang@linux.dev/
v1 -> v2:
* Address sashiko's reviews:
* Fix TOCTOU issue in lwt to avoid changing hdr after checks.
* Add check iph->ihl < 5 in lwt to avoid infinite-loop in MIPS driver.
* Update comment style in selftests with BPF comment style.
* v1: https://lore.kernel.org/bpf/20260525142650.2569-1-leon.hwang@linux.dev/
====================
Link: https://patch.msgid.link/20260602150931.49629-1-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Add two tests to verify the transport header of skb has been set when
encapsulate VxLAN using bpf_lwt_push_encap() helper.
1. VxLAN over IPv4.
2. VxLAN over IPv6.
Without the fix, the tests would fail:
lwt_ip_encap_vxlan:FAIL:transport_hdr offset unexpected transport_hdr offset: actual 70 != expected 20
#208 lwt_ip_encap_vxlan_ipv4:FAIL
lwt_ip_encap_vxlan:FAIL:transport_hdr offset unexpected transport_hdr offset: actual 110 != expected 40
#209 lwt_ip_encap_vxlan_ipv6:FAIL
The unexpected offsets are: outer encap headers
(IPv4: iphdr+udp+vxlan+eth = 50 bytes, IPv6: ipv6hdr+udp+vxlan+eth = 70 bytes)
plus the inner IP header (20 or 40 bytes), because without the fix
transport_header still points at the inner transport layer instead of the
outer UDP header.
Assisted-by: Claude:claude-sonnet-4-6
Cc: Leon Hwang <leon.huangfu@shopee.com>
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260602150931.49629-3-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Currently, bpf_lwt_push_ip_encap() does not update skb->transport_header.
When a driver, e.g. ice, reuses the stale skb->transport_header to
offload checksum computation to NIC hardware, VxLAN packets encapsulated
by bpf_lwt_push_encap() helper may be dropped due to incorrect checksum.
Update skb->transport_header in bpf_lwt_push_ip_encap() whenever the
encapsulated packet uses UDP, so checksum offload works correctly.
Fixes: 52f278774e ("bpf: implement BPF_LWT_ENCAP_IP mode in bpf_lwt_push_encap")
Cc: Leon Hwang <leon.huangfu@shopee.com>
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260602150931.49629-2-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Varun R Mallya says:
====================
RISC-V JIT support for bpf_get_current_task/_btf
These two patches add support for the bpf_get_current_task and
bpf_get_current_task_btf kfuncs in RISC-V JIT and add a selftest.
The first patch adds support for cpu and feature detection on
the JIT disassembly helper function as RISC-V JITed code was not
being disassembled using `LLVMCreateDisasm` as it was missing the
"+c" CPU feature and JITed code contained RISC-V Compressed (C)
Extension. This patch generalizes that to detect CPU features and
enables testing on more RISC-V JIT work ahead.
The second patch, which actually adds this support has been benchmarked
on QEMU RISC-V and shows significant improvements.
It was benchmarked using a simple loop inside a bpf program that ran
bpf_get_current_task() and execution time was measured. It used
bpf_prog_test_run_opts() to repeatedly trigger the BPF program. The loop
ran in 1 second intervals and it kept firing bpf_prog_test_run_opts() as
fast as possible until a second had elapsed and then reported statistics.
====================
Link: https://patch.msgid.link/20260602205847.102825-1-varunrmallya@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
On RISC-V, the current task pointer is stored in the thread pointer
register (tp). Emit a single `mv a5, tp` instead of a full helper
call for BPF_FUNC_get_current_task and BPF_FUNC_get_current_task_btf.
Register bpf_jit_inlines_helper_call() entries for both helpers so the
verifier treats them as inlined, and add the expected `mv a5, tp`
annotation to the riscv64 selftests.
The following show changes before and after this patch.
Before patch:
auipc t1,0x817a # load upper PC-relative address
jalr -2004(t1) # call bpf_get_current_task helper
mv a5,a0 # move return value to BPF_REG_0
After patch:
mv a5,tp # directly: a5 = current (tp = thread pointer)
Benchmark (bpf_prog_test_run wrapping bpf_get_current_task in loop,
batch=100, 10s, QEMU RISC-V):
| runs/sec | helper-calls/sec | ns/call
-------------+-----------+------------------+---------
Before patch | 173,490 | 17,349,090 | 57
After patch | 320,497 | 32,049,780 | 31
-------------+-----------+------------------+---------
Improvement | +84.7% | +84.7% | -45.6%
Signed-off-by: Varun R Mallya <varunrmallya@gmail.com>
Acked-by: Björn Töpel <bjorn@kernel.org>
Link: https://lore.kernel.org/r/20260602205847.102825-3-varunrmallya@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Since there're 4 bytes padding at the end of struct bpf_prog_info, they
won't be checked by bpf_check_uarg_tail_zero().
pahole -C bpf_prog_info ./vmlinux
struct bpf_prog_info {
...
__u32 attach_btf_obj_id; /* 220 4 */
__u32 attach_btf_id; /* 224 4 */
/* size: 232, cachelines: 4, members: 38 */
/* sum members: 224 */
/* sum bitfield members: 1 bits, bit holes: 1, sum bit holes: 31 bits */
/* padding: 4 */
/* forced alignments: 9 */
/* last cacheline: 40 bytes */
} __attribute__((__aligned__(8)));
If a future kernel extension adds a new 4-byte field, older userspace
programs allocating this structure on the stack might inadvertently pass
uninitialized stack garbage into the new field, permanently breaking
backward compatibility. -- sashiko [1]
Fix it by changing sizeof(info) to
offsetofend(struct bpf_prog_info, attach_btf_id).
And, add "__u32 :32" to the tail of struct bpf_prog_info.
[1] https://lore.kernel.org/bpf/20260513224823.6494FC19425@smtp.kernel.org/
Fixes: aba64c7da9 ("bpf: Add verified_insns to bpf_prog_info and fdinfo")
Acked-by: Mykyta Yatsenko <yatsenko@meta.com>
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260605155249.20772-3-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Ricardo B. Marliere says:
====================
selftests/bpf: Tolerate partial builds across kernel configs
Currently the BPF selftests can only be built by using the minimum kernel
configuration defined in tools/testing/selftests/bpf/config*. This poses a
problem in distribution kernels that may have some of the flags disabled or
set as module. For example, we have been running the tests regularly in
openSUSE Tumbleweed [1] [2] but to work around this fact we created a
special package [3] that build the tests against an auxiliary vmlinux with
the BPF Kconfig. We keep a list of known issues that may happen due to,
amongst other things, configuration mismatches [4] [5].
The maintenance of this package is far from ideal, especially for
enterprise kernels. The goal of this series is to enable the common usecase
of running the following in any system:
```sh
make -C tools/testing/selftests install \
SKIP_TARGETS= \
TARGETS=bpf \
BPF_STRICT_BUILD=0 \
O=/lib/modules/$(uname -r)/build
```
As an example, the following script targeting a minimal config can be used
for testing:
```sh
make defconfig
scripts/config --file .config \
--enable DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT \
--enable DEBUG_INFO_BTF \
--enable BPF_SYSCALL \
--enable BPF_JIT
make olddefconfig
make -j$(nproc)
make -j$(nproc) -C tools/testing/selftests install \
SKIP_TARGETS= \
TARGETS=bpf \
BPF_STRICT_BUILD=0
```
This produces a test_progs binary with 592 subtests, against the total of
727. Many of them will still fail or be skipped at runtime due to lack of
symbols, but at least there will be a clear way of building the tests.
[1]: https://openqa.opensuse.org/tests/5811715
[2]: https://openqa.opensuse.org/tests/5811730
[3]: https://src.opensuse.org/rmarliere/kselftests
[4]: https://github.com/openSUSE/kernel-qe/blob/main/kselftests_known_issues.yaml
[5]: https://openqa.opensuse.org/tests/5811730/logfile?filename=run_kselftests-config_mismatches.txt
---
Changes in v12:
- Rebase from 11 to 8 commits: split the test_kmods KDIR patch into a
pure KDIR fix (no PERMISSIVE) and a separate tolerance patch; squash
the BPF_STRICT_BUILD toggle with its first PERMISSIVE user; squash
the four test_progs partial-build patches into one; move the install
fix to immediately follow the first PERMISSIVE user
- Link to v11: https://patch.msgid.link/20260430-selftests-bpf_misconfig-v11-0-e11f7a8c4fdc@suse.com
Changes in v11:
- Gate the BTFIDS pretty-print on $(filter 1,$(V)) so V=0 and V=2 still
print the marker; only V=1 suppresses it (patch 6)
- Use asm volatile ("") in the uprobe_multi_func_{1,2,3} weak stubs to
match the strong definitions in prog_tests/uprobe_multi_test.c
(patch 10)
- Link to v10: https://patch.msgid.link/20260430-selftests-bpf_misconfig-v10-0-cd302a31af16@suse.com
Changes in v10:
- Drop $(wildcard $^) from the bench link recipe so cc fails cleanly on
the first missing input and the || fallback emits one SKIP-LINK line
instead of a wall of undefined-reference errors; also makes make -n
accurate (patch 9)
- Include <alloca.h> in testing_helpers.c for alloca() (patch 10)
- Link to v9: https://patch.msgid.link/20260429-selftests-bpf_misconfig-v9-0-c311f06b4791@suse.com
Changes in v9:
- Also pass KBUILD_OUTPUT=$(KMOD_O_VALID) when invoking kbuild so an
inherited command-line KBUILD_OUTPUT cannot disagree with O= (patch 2)
- Note BPFOBJ remains a normal prereq intentionally (patch 5)
- Sub-shell isolate cd/CC and use $@ for $(RM); gate the BTFIDS
pretty-print on $(V) so verbose mode does not double-print (patch 6)
- Restrict permissive compile-failure tolerance and partial-link to
test_progs%; runners with strong cross-object references (test_maps)
keep strict semantics (patches 6 and 8)
- Link to v8: https://patch.msgid.link/20260428-selftests-bpf_misconfig-v8-0-bf02cf97dbcb@suse.com
Changes in v8:
- In permissive mode, keep source changes to already-built tests
triggering relinks, while using recipe-time $(wildcard ...) to pick
up fresh .test.o files without duplicate linker inputs (patch 8)
- Resolve relative O=/KBUILD_OUTPUT before recursing into test_kmods,
and only treat it as a kernel build dir when it contains
Module.symvers (patch 2)
- Note in the commit message that PERMISSIVE-mode bisecting here needs
the next two patches (patch 6)
- Clarify in the commit message that order-only skeleton prereqs do not
break the new-skel-via-local-header case (patch 5)
- Exclude not-built tests from the success count so summary and JSON
report them only as skipped (patch 7)
- Tighten commit messages for accuracy and clarity
- Link to v7: https://patch.msgid.link/20260416-selftests-bpf_misconfig-v7-0-a078e18012e4@suse.com
Changes in v7:
- Use $(abspath) for KMOD_O so relative O= paths resolve correctly
when make -C changes directory (patch 2)
- Guard make clean against missing KDIR unconditionally; there is
nothing to clean when kernel headers are absent (patch 2)
- Drop explicit $(TRUNNER_TEST_OBJS) from linker filter in strict mode;
$^ already contains them as normal prerequisites (patch 8)
- Link to v6: https://patch.msgid.link/20260416-selftests-bpf_misconfig-v6-0-7efeab504af1@suse.com
Changes in v6:
- Add --ignore-missing-args to -extras rsync so out-of-tree permissive
builds do not abort when .ko files are absent (patch 2)
- Use $(abspath) for KMOD_O so relative O= paths resolve correctly
when make -C changes directory (patch 2)
- Guard make clean against missing KDIR unconditionally so cleaning
does not abort when kernel headers are absent (patch 2)
- Remove stale skeleton headers in early-exit paths when .bpf.o is
missing on incremental builds (patch 3)
- Fix strict-mode skeleton rules: use && before temp file cleanup so
bpftool failures are not masked by rm -f exit code (patch 3)
- Track test filter selection separately from not_built so -t/-n flags
are respected for unbuilt tests (patch 7)
- Make TRUNNER_TEST_OBJS order-only only in permissive mode, preserving
incremental relinking in strict builds (patch 8)
- Drop explicit $(TRUNNER_TEST_OBJS) from linker filter in strict mode;
they are already in $^ as normal prerequisites (patch 8)
- Reorder: move skip-unbuilt-tests patch before partial-linking patch
for bisectability
- Link to v5: https://patch.msgid.link/20260415-selftests-bpf_misconfig-v5-0-03d0a52a898a@suse.com
Changes in v5:
- Add BPF_STRICT_BUILD toggle as patch 1 so every subsequent patch
gates tolerance behind PERMISSIVE from the start, making the series
bisectable with strict-by-default at every point
- Fix O= commit message; make parent cp conditional (patch 2)
- Tolerate linked skeleton failures (patch 3)
- Skip feature detection for emit_tests (patch 4)
- Clarify bench is all-or-nothing in commit message (patch 8)
- Move stack_mprotect() to testing_helpers.c, drop weak stubs (patch 9)
- Report not-built tests as "SKIP (not built)" in output (patch 10)
- Drop overly broad 2>/dev/null || true from install rsync; rely solely
on --ignore-missing-args which already handles absent files (patch 11)
- Link to v4: https://patch.msgid.link/20260406-selftests-bpf_misconfig-v4-0-9914f50efdf7@suse.com
Changes in v4:
- Drop the test_kmods kselftest module flow patch: lib.mk gen_mods_dir
invokes $(MAKE) -C $(TEST_GEN_MODS_DIR) without forwarding
RESOLVE_BTFIDS, breaking ASAN and GCC BPF CI builds (Makefile.modfinal
cannot find resolve_btfids in the kbuild output tree)
- Link to v3:
https://patch.msgid.link/20260406-selftests-bpf_misconfig-v3-0-587a1114263c@suse.com
Changes in v3:
- Split test_kmods patch into two: fix KDIR handling (O= passthrough,
EXTRA_CFLAGS/EXTRA_LDFLAGS clearing) and wire into lib.mk via
TEST_GEN_MODS_DIR
- Pass O= through to the kernel module build so artifacts land in the
output tree, not the source tree
- Clear EXTRA_CFLAGS and EXTRA_LDFLAGS when invoking the kernel build to
prevent host flags (e.g. -static) leaking into module compilation
- Replace the bespoke test_kmods pattern rule with lib.mk module
infrastructure (TEST_GEN_MODS_DIR); lib.mk now drives build and clean
lifecycle
- Make the .ko copy step resilient: emit SKIP instead of failing when a
module is absent
- Expand the uprobe weak stub comment in bpf_cookie.c to explain why
noinline is required
- Link to v2:
https://patch.msgid.link/20260403-selftests-bpf_misconfig-v2-0-f06700380a9d@suse.com
Changes in v2:
- Skip test_kmods build/clean when KDIR directory does not exist
- Use `Module.symvers` instead of `.config` for in-tree detection
- Fix skeleton order-only prereqs commit message
- Guard BTFIDS step when .test.o is absent
- Add `__weak stack_mprotect()` stubs in `bpf_cookie.c` and `iters.c`
- Link to v1:
https://patch.msgid.link/20260401-selftests-bpf_misconfig-v1-0-3ae42c0af76f@suse.com
Assisted-by: {codex,claude}
Tested-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Ricardo B. Marliere <rbm@suse.com>
---
Ricardo B. Marlière (11):
selftests/bpf: Add BPF_STRICT_BUILD toggle
selftests/bpf: Fix test_kmods KDIR to honor O= and distro kernels
selftests/bpf: Tolerate BPF and skeleton generation failures
selftests/bpf: Avoid rebuilds when running emit_tests
selftests/bpf: Make skeleton headers order-only prerequisites of .test.d
selftests/bpf: Tolerate test file compilation failures
selftests/bpf: Skip tests whose objects were not built
selftests/bpf: Allow test_progs to link with a partial object set
selftests/bpf: Tolerate benchmark build failures
selftests/bpf: Provide weak definitions for cross-test functions
selftests/bpf: Tolerate missing files during install
tools/testing/selftests/bpf/Makefile | 177 ++++++++++++++-------
.../testing/selftests/bpf/prog_tests/bpf_cookie.c | 17 +-
tools/testing/selftests/bpf/prog_tests/iters.c | 2 -
tools/testing/selftests/bpf/prog_tests/test_lsm.c | 22 ---
tools/testing/selftests/bpf/test_kmods/Makefile | 30 +++-
tools/testing/selftests/bpf/test_progs.c | 53 +++++-
tools/testing/selftests/bpf/test_progs.h | 1 +
tools/testing/selftests/bpf/testing_helpers.c | 18 +++
tools/testing/selftests/bpf/testing_helpers.h | 1 +
9 files changed, 226 insertions(+), 95 deletions(-)
---
base-commit: b93c55b493
change-id: 20260401-selftests-bpf_misconfig-4c33ef5c56da
Best regards,
--
Ricardo B. Marlière <rbm@suse.com>
====================
Link: https://patch.msgid.link/20260602-selftests-bpf_misconfig-v12-0-27f898b3ba26@suse.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
With partial builds, some TEST_GEN_FILES entries can be absent at install
time. rsync treats missing source arguments as fatal and aborts kselftest
installation.
Override INSTALL_SINGLE_RULE in selftests/bpf to use --ignore-missing-args,
while keeping the existing bpf-specific INSTALL_RULE extension logic. Also
add --ignore-missing-args to the TEST_INST_SUBDIRS rsync loop so that
subdirectories with no .bpf.o files (e.g. when a test runner flavor was
skipped) do not abort installation.
Note that the INSTALL_SINGLE_RULE override applies globally to all file
categories including static source files (TEST_PROGS, TEST_FILES). These
are version-controlled and should always be present, so the practical risk
is negligible.
Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
Link: https://lore.kernel.org/r/20260602-selftests-bpf_misconfig-v12-11-27f898b3ba26@suse.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Some test files reference functions defined in other translation units that
may not be compiled when skeletons are missing. Replace forward
declarations of uprobe_multi_func_{1,2,3}() with weak no-op stubs so the
linker resolves them regardless of which objects are present.
The stub bodies are `asm volatile ("")` rather than empty, matching the
shape of the strong definitions in prog_tests/uprobe_multi_test.c. This
keeps the weak and strong sides on the same footing for the optimiser
(noinline + asm-barrier), which is the form upstream already relies on
for these functions.
Move stack_mprotect() from test_lsm.c into testing_helpers.c so it is
always available. The previous weak-stub approach returned 0, which would
cause callers expecting -1/EPERM to fail their assertions
deterministically. Having the real implementation in a shared utility
avoids this problem entirely.
Include <alloca.h> for alloca() so the build does not rely on glibc's
implicit declaration via <stdlib.h>.
Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
Link: https://lore.kernel.org/r/20260602-selftests-bpf_misconfig-v12-10-27f898b3ba26@suse.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Benchmark objects depend on skeletons that may be missing when some BPF
programs fail to build. In that case, benchmark object compilation or final
bench linking should not abort the full selftests/bpf build.
Keep both steps non-fatal, emit SKIP-BENCH or SKIP-LINK, and remove failed
outputs so stale objects or binaries are not reused by later incremental
builds. Note that because bench.c statically references every benchmark via
extern symbols, partial linking is not possible: if any single benchmark
object fails, the entire bench binary is skipped. This is by design -- the
error handler catches all compilation failures including genuine ones, but
those are caught by full-config CI runs.
Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
Link: https://lore.kernel.org/r/20260602-selftests-bpf_misconfig-v12-9-27f898b3ba26@suse.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
When individual test files are skipped due to compilation failures, their
.test.o files are absent. The linker step currently lists all expected
.test.o files as explicit prerequisites, so make considers any missing one
an error.
In permissive mode, declare the test objects that already exist on disk
(via parse-time $(wildcard ...)) as normal prerequisites of the binary so
that modifications to a test source still trigger a relink, and keep the
full TRUNNER_TEST_OBJS list as order-only prerequisites so that initial
fresh builds still produce them and missing objects do not abort the link.
The recipe filter is split per mode: in permissive mode it combines a
recipe-time $(wildcard ...) (which catches objects freshly produced via
the order-only path on a fresh build) with $(filter-out
$(TRUNNER_TEST_OBJS),$^) (which keeps the non-test inputs from $^ but
drops the parse-time wildcard duplicates). This avoids passing the same
.test.o twice to the linker while still presenting test objects before
libbpf.a so that GNU ld, which scans static archives left-to-right, pulls
in archive members referenced exclusively by test objects (e.g.
ring_buffer__new from ringbuf.c). In default (strict) mode the recipe
remains the simple $(filter %.a %.o,$^) since TRUNNER_TEST_OBJS is part
of $^ exactly once.
Gate the partial-link behavior on $(if $(filter test_progs%,$1),...) so
it only applies to test_progs and its flavors. test_maps and similar
runners using strong cross-object references would link-fail with a
partial set and intentionally retain strict link semantics.
Note: adding a brand-new test_*.c file in permissive mode requires
removing the binary (or a clean rebuild) before the new test is linked
in, because the parse-time $(wildcard ...) is evaluated when the Makefile
is read and will not yet see the new .test.o. This is acceptable since
permissive mode targets tolerant CI builds rather than incremental
development.
Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
Link: https://lore.kernel.org/r/20260602-selftests-bpf_misconfig-v12-8-27f898b3ba26@suse.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
When both run_test and run_serial_test are NULL (because the corresponding
.test.o was not compiled), mark the test as not built instead of fatally
aborting.
Report these tests as "SKIP (not built)" in per-test output and include
them in the skip count so they remain visible in CI results and JSON
output. The summary line shows the not-built count when nonzero:
Summary: 50/55 PASSED, 5 SKIPPED (3 not built), 0 FAILED
Tests filtered out by -t/-n remain invisible as before; only genuinely
unbuilt tests are surfaced.
Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
Link: https://lore.kernel.org/r/20260602-selftests-bpf_misconfig-v12-7-27f898b3ba26@suse.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Individual test files may fail to compile when headers or kernel features
required by that test are absent. Currently this aborts the entire build.
Make the per-test compilation non-fatal: remove the output object on
failure and print a SKIP-TEST marker to stderr. Guard the BTFIDS
post-processing step so it is skipped when the object file is absent. The
linker step will later ignore absent objects, allowing the remaining tests
to build and run.
Group cd and CC in a sub-shell so a cd failure cannot leak into the
error-handling branch and operate in the original working directory; use
$@ (absolute path) for $(RM) so it cannot match an unrelated file there.
Replace the $(call msg,...) in the BTFIDS block with a plain printf
(the msg macro expands to @printf, which is a make-recipe construct and
is invalid inside a shell if-then-fi body) and gate the printf on
$(filter 1,$(V)) so verbose mode (V=1) does not double-print the line
that the recipe shell already echoes; non-verbose modes (V unset, V=0,
V=2, ...) still print the BTFIDS marker, matching the convention of the
shared msg macro.
Restrict tolerance to test_progs and its flavors via an inlined
$(if $(filter test_progs%,$1),$(if $(PERMISSIVE),...)) check: runners
with strong cross-object references (e.g. test_maps) would link-fail
with a partial object set, so they keep strict semantics even when
BPF_STRICT_BUILD=0. The check is inlined rather than stored in a helper
variable so $1 is substituted at $(call) time and the per-runner result
is baked into each recipe.
Note on bisectability: this change is gated entirely behind PERMISSIVE
for test_progs%, so default builds (BPF_STRICT_BUILD!=0) compile and
run identically at every commit in the series. Bisecting in PERMISSIVE
mode at this commit still requires the next two patches ("selftests/bpf:
Skip tests whose objects were not built" and "selftests/bpf: Allow
test_progs to link with a partial object set") to avoid the linker
rejecting missing objects and the runtime aborting on NULL function
pointers.
Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
Link: https://lore.kernel.org/r/20260602-selftests-bpf_misconfig-v12-6-27f898b3ba26@suse.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
The .test.d dependency files are generated by the C preprocessor and list
the headers each test file actually #includes. Skeleton headers appear in
those generated lists, so the .test.o -> .skel.h dependency is already
tracked by the .d file content.
Making skeletons order-only prerequisites of .test.d means that a missing
or skipped skeleton does not prevent .test.d generation, and regenerating a
skeleton does not force .test.d to be recreated. This avoids unnecessary
recompilation and, more importantly, avoids build errors when a skeleton
was intentionally skipped due to a BPF compilation failure.
$$(BPFOBJ) is intentionally kept as a normal prerequisite: a libbpf
rebuild legitimately invalidates .test.d, since libbpf header changes
can affect the headers .test.o sees. Only the skeleton headers are
moved to order-only.
Note that adding a new BPF skeleton via a modified existing local header
still works correctly: GNU make builds order-only prerequisites that do
not exist (the order-only qualifier only suppresses timestamp-driven
rebuilds, not existence-driven builds), so a brand-new .skel.h listed in
TRUNNER_BPF_SKELS is generated even when .test.d is otherwise up to date.
The modified local header invalidates .test.o through the previously
included .d content, forcing a recompile that regenerates .test.d with
the new .skel.h dependency captured by gcc -MMD.
Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
Link: https://lore.kernel.org/r/20260602-selftests-bpf_misconfig-v12-5-27f898b3ba26@suse.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
emit_tests is used while installing selftests to generate the kselftest
list. Pulling in .d files for this goal can trigger BPF rebuild rules and
mix build output into list generation.
Skip dependency file inclusion for emit_tests, like clean goals, so list
generation stays side-effect free. Also add emit_tests to
NON_CHECK_FEAT_TARGETS so that feature detection is skipped; without this,
Makefile.feature's $(info) output leaks into stdout and corrupts the test
list captured by the top-level selftests Makefile.
Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
Link: https://lore.kernel.org/r/20260602-selftests-bpf_misconfig-v12-4-27f898b3ba26@suse.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Some BPF programs cannot be built on distro kernels because required BTF
types or features are missing. A single failure currently aborts the
selftests/bpf build.
Make BPF object and skeleton generation best effort in permissive mode:
emit SKIP-BPF or SKIP-SKEL to stderr, remove failed outputs so downstream
rules can detect absence, and continue with remaining tests. Apply the same
tolerance to linked skeletons (TRUNNER_BPF_SKELS_LINKED), which depend on
multiple .bpf.o files and abort the build when any dependency is missing.
Note that progress messages (GEN-SKEL, LINK-BPF) are also redirected to
stderr as a side effect of rewriting the recipes into single-shell
pipelines; the $(call msg,...) macro is a make-recipe construct that cannot
be used inside an &&-chained shell command sequence.
Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
Link: https://lore.kernel.org/r/20260602-selftests-bpf_misconfig-v12-3-27f898b3ba26@suse.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
test_kmods/Makefile always pointed KDIR at the kernel source tree root,
ignoring O= and KBUILD_OUTPUT. On distro kernels where the source tree has
not been built, the Makefile had no fallback and would fail
unconditionally.
When O= or KBUILD_OUTPUT is set and points at a prepared kernel build
directory (one containing Module.symvers), pass it through so kbuild can
locate the correct build infrastructure (scripts, Kconfig, etc.). Note
that the module artifacts themselves still land in the M= directory,
which is test_kmods/; O= only controls where kbuild finds its build
infrastructure. Fall back to /lib/modules/$(uname -r)/build when neither
an explicit valid build directory nor an in-tree Module.symvers is
present.
A selftests-only O= value (one that does not contain Module.symvers, e.g.
a private output directory) is intentionally not treated as a kernel
build directory. Without this guard, a user invoking
"make -C tools/testing/selftests/bpf O=/tmp/out" would have test_kmods
try to use /tmp/out as the kernel build dir and fail.
The parent bpf/Makefile resolves O= and KBUILD_OUTPUT to absolute paths
before invoking the test_kmods sub-make. Without this, $(abspath ...)
inside test_kmods/Makefile would resolve relative paths against the
sub-make's CWD (test_kmods/) rather than the user's invocation directory.
When O= is passed to kbuild, also pass KBUILD_OUTPUT=$(KMOD_O_VALID)
explicitly. The parent invocation lifts KBUILD_OUTPUT into MAKEFLAGS as
a command-line variable, which would otherwise suppress kbuild's own
"KBUILD_OUTPUT := $(O)" assignment and cause it to use the inherited
KBUILD_OUTPUT instead of the validated O=.
Guard both all and clean against a missing KDIR so the step is silently
skipped rather than fatal. Make the parent Makefile's cp conditional so it
does not abort when modules were not built.
Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
Link: https://lore.kernel.org/r/20260602-selftests-bpf_misconfig-v12-2-27f898b3ba26@suse.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Distro kernels often lack BTF types or kernel features required by some BPF
selftests, causing the build to abort on the first failure and preventing
the remaining tests from running.
Add BPF_STRICT_BUILD (default 1) to control build failure tolerance. When
set to 0, the PERMISSIVE make variable is assigned a non-empty value that
subsequent Makefile rules use to make individual build steps non-fatal.
When set to 1 (the default), the build fails on any error, preserving the
existing behavior for CI and direct builds.
Users can opt in to permissive mode on the command line:
make -C tools/testing/selftests \
TARGETS=bpf SKIP_TARGETS= BPF_STRICT_BUILD=0
Suggested-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
Link: https://lore.kernel.org/r/20260602-selftests-bpf_misconfig-v12-1-27f898b3ba26@suse.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
bpf_rb_root_free() detaches the root by copying the current rb_root_cached
and then replacing the live root with RB_ROOT_CACHED. It then walks the
copied root and drops each object contained in the tree.
This leaves the rb node state intact while dropping the object. If the
object is refcounted and survives the drop, its bpf_rb_node_kern still
contains an owner pointer to the freed root and stale rb tree linkage. If
a later bpf_rb_root allocation reuses the same address, bpf_rbtree_remove()
can incorrectly pass the owner check and call rb_erase_cached() on a node
whose rb pointers belong to the old tree.
Mirror the list draining behavior by marking nodes as busy while the root
is being detached, then clear the rb node and release the owner before
dropping the containing object. This makes surviving nodes unowned and
safe to reject from remove or accept for a later add.
Fixes: 9c395c1b99 ("bpf: Add basic bpf_rb_{root,node} support")
Signed-off-by: Kaitao Cheng <chengkaitao@kylinos.cn>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20260605094143.5509-1-kaitao.cheng@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
use_file_dynptr_slice_after_put_file() reads the dynptr via
bpf_dynptr_data(), which always returns NULL for a read-only file
dynptr, making the example confusing. Switch to bpf_dynptr_slice(), the
correct read API for file dynptrs, and read (rather than write) the slice
since it is read-only. The test still fails as expected.
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Amery Hung <ameryhung@gmail.com>
Link: https://lore.kernel.org/r/20260605202056.1780352-6-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
check_ids() warned when it ran out of idmap slots, assuming this was
impossible because the slots are bounded by the number of registers and
stack slots. That assumption no longer holds: referenced dynptrs acquire
an intermediate reference that lives in refs[] but is not backed by any
register or stack slot [0], so a program can accumulate more reference
ids than the idmap can hold and exhaust it.
Exhaustion is fine for verification correctness. check_ids() already
returns false, which makes the states compare as not equivalent and
prevents unsound pruning. The only effect of the WARN_ON_ONCE() is log
noise, or a panic under panic_on_warn. Drop the warning and keep
returning false.
[0] 308c7a0ae8 ("bpf: Refactor object relationship tracking and fix dynptr UAF bug")
Signed-off-by: Amery Hung <ameryhung@gmail.com>
Link: https://lore.kernel.org/r/20260605202056.1780352-5-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
refsafe() compared each reference's id and type but not its parent_id,
so two states whose PTR references differ only in the parent object they
were derived from could be wrongly treated as equivalent and pruned. Fix
it by checking parent_id too.
Fixes: 308c7a0ae8 ("bpf: Refactor object relationship tracking and fix dynptr UAF bug")
Signed-off-by: Amery Hung <ameryhung@gmail.com>
Link: https://lore.kernel.org/r/20260605202056.1780352-4-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
When acquiring references for struct_ops program arguments tagged with
"__ref", the return value of acquire_reference() was stored directly
into u32 ctx_arg_info[i].ref_id without checking for failure.
acquire_reference() returns -ENOMEM when acquire_reference_state() fails
to allocate, so the error was silently stored as a ref_id instead of
aborting verification. Fix it by checking the return.
Fixes: a687df2008 ("bpf: Support getting referenced kptr from struct_ops argument")
Signed-off-by: Amery Hung <ameryhung@gmail.com>
Link: https://lore.kernel.org/r/20260605202056.1780352-3-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
acquire_reference() returns a signed int that may be a negative errno
but was converted to unsigned, which makes the subsequent error check
deadcode. Fix it by declaring 'id' as int so the error path is taken
correctly.
Fixes: 308c7a0ae8 ("bpf: Refactor object relationship tracking and fix dynptr UAF bug")
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Amery Hung <ameryhung@gmail.com>
Link: https://lore.kernel.org/r/20260605202056.1780352-2-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
When the perf build executes 'make -C ../bpf/bpftool bootstrap', bpftool's
Makefile unconditionally evaluated feature checks for llvm, libcap, libbfd,
and disassembler libraries because the bootstrap target was not exempted.
Since the bootstrap bpftool strictly compiles minimal AST parsing and C
code generation logic without linking LLVM or disassembler libraries, these
feature check sub-makes are completely redundant.
Exempt the bootstrap target from non-essential feature tests to eliminate
unneeded sub-make fork overhead during Kbuild startup.
Tested-by: James Clark <james.clark@linaro.org>
Assisted-by: Gemini:gemini-3.1-pro-preview
Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Quentin Monnet <qmo@kernel.org>
Link: https://lore.kernel.org/r/20260531010750.525160-1-irogers@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
apply_range_set_cb() maps the pages for a new arena allocation and returned
-EBUSY when the target PTE was already populated. Kernel-fault recovery
leaves the per-arena scratch page in unallocated arena PTEs, so a later
bpf_arena_alloc_pages() over such a page hits that -EBUSY, and every
subsequent allocation of it fails the same way. Allocation must install the
real page over scratch instead.
Overwriting the scratch PTE in place is a valid->valid change, which arm64
forbids without break-before-make. Route through an invalid entry instead:
ptep_try_set() fills only a none slot, so the PTE goes scratch->none->page.
On finding scratch, clear it and flush_tlb_before_set() before retrying. The
new flush_tlb_before_set() is a no-op except on arches like arm64 that need
the break-before-make TLB invalidate. The loop also copes with a concurrent
fault re-scratching the slot.
Arches without ptep_try_set() never install the scratch page, so keep the
must-be-empty check and set_pte_at() for them.
Fixes: dc11a4dba2 ("bpf: Recover arena kernel faults with scratch page")
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260601183728.1800490-1-tj@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Devmap broadcast redirects clone the packet for all but the last
destination.
For native XDP, that clone path copies only the linear xdp_frame data,
while fragmented frames keep skb_shared_info in tailroom outside the
linear area. Cloning such a frame leaves XDP_FLAGS_HAS_FRAGS set but
without valid frag metadata, and the later free path can interpret
uninitialized tail data as skb_shared_info, leading to an out-of-bounds
access during frame return.
Reject fragmented native XDP frames in dev_map_enqueue_clone().
Add the same restriction to the generic XDP clone path in
dev_map_redirect_clone(). Generic XDP represents fragmented packets as
nonlinear skbs, and rejecting them here keeps clone-based broadcast
support aligned between native and generic XDP.
Fixes: e624d4ed4a ("xdp: Extend xdp_redirect_map with broadcast support")
Cc: stable@kernel.org
Reported-by: Yuan Tan <yuantan098@gmail.com>
Reported-by: Zhengchuan Liang <zcliangcn@gmail.com>
Reported-by: Xin Liu <bird@lzu.edu.cn>
Assisted-by: Codex:GPT-5.4
Signed-off-by: Zhao Zhang <zzhan461@ucr.edu>
Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/r/21c2d153dd25603d359069a02bf06779b51f6423.1780385378.git.zzhan461@ucr.edu
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Mykyta Yatsenko says:
====================
bpf: Introduce resizable hash map
This patch series introduces BPF_MAP_TYPE_RHASH, a new hash map type that
leverages the kernel's rhashtable to provide resizable hash map for BPF.
The existing BPF_MAP_TYPE_HASH uses a fixed number of buckets determined at
map creation time. While this works well for many use cases, it presents
challenges when:
1. The number of elements is unknown at creation time
2. The element count varies significantly during runtime
3. Memory efficiency is important (over-provisioning wastes memory,
under-provisioning hurts performance)
BPF_MAP_TYPE_RHASH addresses these issues by using rhashtable, which
automatically grows and shrinks based on load factor.
The implementation wraps the kernel's rhashtable with BPF map operations:
- Uses bpf_mem_alloc for RCU-safe memory management
- Supports all standard map operations (lookup, update, delete, get_next_key)
- Supports batch operations (lookup_batch, lookup_and_delete_batch)
- Supports BPF iterators for traversal
- Supports BPF_F_LOCK for spin locks in values
- Requires BPF_F_NO_PREALLOC flag (elements allocated on demand)
- In-place updates for improved performance.
- max_entries serves as a hard limit, not bucket count
- Uses bit_spin_lock() + local_irq_save() for bucket locking,
similar to existing BPF hashmap's raw_spin_lock_irqsave(), insertions and
deletes may fail.
- Iterations are best-effort, if resize, insertions, deletions take place
concurrently, iterations may visit same elements multiple times or skip
elements.
- Lock out insertions, when running special fields destructor to guarantee
its completion.
The series includes comprehensive tests:
- Basic operations in test_maps (lookup, update, delete, get_next_key)
- BPF program tests for lookup/update/delete semantics
- Seq file tests
Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
---
Update implementation
---------------------
Current implementation of the BPF_MAP_TYPE_RHASH does not provide
the same strong guarantees on the values consistency under concurrent
reads/writes as BPF_MAP_TYPE_HASH.
BPF_MAP_TYPE_HASH allocates a new element and atomically swaps the
pointer. BPF_MAP_TYPE_RHASH does memcpy in place with no lock held.
rhash trades consistency for speed, concurrent readers can observe
partially updated data. Two concurrent writers to the same key can
also interleave, producing mixed values. This is similar to arraymap
update implementation, including handling of the special fields.
As a solution, user may use BPF_F_LOCK to guarantee consistent reads
and write serialization.
Summary of the read consistency guarantees:
map type | write mechanism | read consistency
-------------+------------------+--------------------------
htab | alloc, swap ptr | always consistent (RCU)
htab F_LOCK | in-place + lock | consistent if reader locks
-------------+------------------+--------------------------
rhtab | in-place memcpy | torn reads
rhtab F_LOCK | in-place + lock | consistent if reader locks
Benchmarks
----------
1. LOOKUP (single producer, M events/sec)
key | max | nr | htab | rhtab | ratio | delta
----+-----+-------+---------+---------+-------+-------
8 | 1K | 750 | 99.85 | 81.92 | 0.82x | -18 %
8 | 1K | 1K | 100.71 | 80.19 | 0.80x | -20 %
8 | 1M | 750K | 23.37 | 72.09 | 3.08x | +208 %
8 | 1M | 1M | 13.39 | 53.72 | 4.01x | +301 %
32 | 1K | 750 | 51.57 | 42.78 | 0.83x | -17 %
32 | 1K | 1K | 50.81 | 45.83 | 0.90x | -10 %
32 | 1M | 750K | 11.27 | 15.29 | 1.36x | +36 %
32 | 1M | 1M | 7.32 | 8.75 | 1.19x | +19 %
256 | 1K | 750 | 7.58 | 7.88 | 1.04x | +4 %
256 | 1K | 1K | 7.43 | 7.81 | 1.05x | +5 %
256 | 1M | 750K | 3.69 | 4.27 | 1.16x | +16 %
256 | 1M | 1M | 2.60 | 3.12 | 1.20x | +20 %
Pattern:
* Small map (1K): htab wins for 8 / 32 byte keys by 10-20 %
because the preallocated bucket array fits in L1. Equalises
at 256 byte keys.
* Large map (1M): rhtab wins everywhere, up to 4x at high load
factor with 8 byte keys.
* Higher load factor amplifies rhtab's lead: rhtab grows the
bucket array; htab stays at user-declared max.
2. FULL UPDATE (M events/sec per producer, -p 7)
htab per-producer:
20.33 22.02 19.27 23.61 24.18 23.17 21.07
mean 21.94 range 19.27 - 24.18
rhtab per-producer:
133.51 129.47 74.52 129.29 102.26 129.98 107.64
mean 115.24 range 74.52 - 133.51
speedup (mean): 5.25x (+425 %)
In-place memcpy avoids the per-update alloc + RCU pointer swap
that htab pays.
3. MEMORY (overwrite, -p 8, no --preallocated)
value_size | htab ops/s | rhtab ops/s | htab mem | rhtab mem
-----------+-------------+-------------+----------+----------
32 B | 122.87 k/s | 133.04 k/s | 2.47 MiB | 2.49 MiB
4096 B | 64.43 k/s | 65.38 k/s | 6.74 MiB | 6.44 MiB
rhtab/htab : +8 % ops, +0.8 % mem (32 B)
+1 % ops, -4 % mem (4096 B)
SUMMARY
* Small / well-fitting map: htab is faster (cache-friendly
fixed bucket array), but only by ~10-20 %.
* Large / high-load-factor map: rhtab is dramatically faster
(1.2x to 4x) because rhashtable resizes to keep the load
factor sane while htab stays stuck at user-declared max.
* Update-heavy workloads: rhtab is ~5x faster per producer
via in-place memcpy.
* Memory benchmark: effectively on par
---
Changes in v7:
- rhashtable_next_key: move into lib/rhashtable.c, drop params argument
(Herbert).
- rhashtable_next_key: kdoc clarifies that behavior on tables with
duplicate keys is undefined (sashiko).
- rhashtable: include Herbert's "Use irq work for shrinking" patch so
__rhashtable_remove_fast_one() can fire the shrink path from NMI
context (Herbert).
- hashtab: fix u32 multiply overflow in __rhtab_map_lookup_and_delete_batch
copy_to_user; cast total to size_t before multiplying by key_size /
value_size (sashiko, bot+bpf-ci).
- hashtab: allow kptr/refcount fields in rhtab values (same model as
array map).
- Link to v6: https://patch.msgid.link/20260602-rhash-v6-0-1bfd35a4184f@meta.com
Changes in v6:
- rhashtable_next_key: advance past duplicate keys in the main bucket
chain to avoid an infinite loop when there are duplicate keys
(sashiko).
- rhashtable_next_key: return ERR_PTR(-EOPNOTSUPP) on rhltable (sashiko).
- rhashtable: selftest pre-sizes the table to avoid concurrent rehash
triggering spurious failures (sashiko).
- hashtab: real rhtab_map_mem_usage in the basic commit; move
bpf_map_free_internal_structs from rhtab_free_elem into the
special-fields commit where it does meaningful work (bot+bpf-ci).
- bpf_iter (seq_file): switch to rhashtable_walk_* for stronger
coverage under concurrent rehash; get_next_key and batch keep
rhashtable_next_key (sashiko).
- iter ops: rhtab_map_get_next_key adds IS_ERR check
before dereferencing the element pointer (sashiko).
- iter ops: bpf_each_rhash_elem removes cond_resched() (sashiko).
- iter ops: batch returns -EAGAIN (not -ENOENT) on cursor delete,
so userspace can distinguish lost cursor from end-of-iteration
and restart from NULL (sashiko).
- Link to v5: https://patch.msgid.link/20260528-rhash-v5-0-7205191b6c57@meta.com
Changes in v5:
- rhashtable_next_key: add kdoc WARNING to highlight lack of rehash
detection and unbounded iteration (Herbert).
- rhashtable: selftest now checks IS_ERR() before PTR_ERR comparison
on the missing-key path (bot+bpf-ci).
- hashtab: drop dead stub bodies and unused map_ops registrations
from the basic commit; iteration commit adds bodies, structs, and
registrations together. .map_get_next_key keeps a stub registration
in the basic commit because the syscall dispatcher does not
NULL-check it; iteration commit replaces the stub body with the
real implementation (bot+bpf-ci).
- hashtab: fix batch cursor advancement. v4 stashed the lookahead
element key but then resumed via next_key(cursor), skipping that
element across batch boundaries and orphaning it on
lookup_and_delete_batch. v5 stashes the lookahead key and looks
it up directly on the next batch entry (bot+bpf-ci, sashiko v3).
- hashtab: document torn-read race in rhtab_map_update_existing,
matching arraymap semantics (bot+bpf-ci).
- Link to v4: https://patch.msgid.link/20260513-rhash-v4-0-dd3d541ccb0b@meta.com
Changes in v4:
- rhashtable: introduce rhashtable_next_key(), drop walker-based
iteration for BPF (also drops earlier rhashtable_walk_enter_from()
proposal).
- map_extra: presize hint via lower 32 bits (nelem_hint), capped at
U16_MAX.
- Automatic shrinking enabled (was missing despite being advertised).
- Reject key_size > U16_MAX (rhashtable_params.key_len is u16).
- Replace irqs_disabled() guard with bpf_disable_instrumentation around
bucket-lock paths: closes same-CPU NMI tracing recursion without
rejecting legitimate IRQ-context callers.
- lookup_and_delete reordered: unlink before copy to avoid populating
user buffer on concurrent-unlink -ENOENT.
- update_existing reordered: copy then free_fields, matching arraymap.
- Word-sized key fast path (sizeof(long) bytes), inlined hashfn/cmpfn
via static-const rhashtable_params; works on both 32-bit and 64-bit.
- check_and_init_map_value() on insert (zero special-field bytes from
recycled bpf_mem_alloc memory; previously bpf_spin_lock could read
garbage and qspinlock would deadlock).
- BPF_SPIN_LOCK / BPF_RES_SPIN_LOCK allowlist moved to the special-
fields commit so each commit is bisect-safe.
- Link to v3: https://patch.msgid.link/20260424-rhash-v3-0-d0fa0ce4379b@meta.com
Changes in v3:
- Squash all commits implementing basic functions into one (Alexei)
- Remove selftests that were not necessary (Alexei)
- Resize detection for kernel full iterations, error out on resize (Alexei)
- Remove second lookup in get_next_key() (Emil)
- __acquires(RCU)/__releases(RCU) on seq_start/seq_stop (Emil)
- Use bpf_map_check_op_flags() where it makes sense (Leon)
- Benchmarks refresh, experiment with alternative hash functions
- Rely on iterator invalidation during rehash to handle table resizes:
fail on resize where we fully iterate on table inside kernel, dont fail on
resize where iteration goes through userspace. Exception -
rhtab_map_free_internal_structs() should be just safe to iterate fully
in kernel, no risk of infinite loop, because no user holding reference.
- Handle special fields during in-place updates (Emil, sashiko)
- Link to v2: https://lore.kernel.org/all/20260408-rhash-v2-0-3b3675da1f6e@meta.com/
Changes in v2:
- Added benchmarks
- Reworked all functions that walk the rhashtable, use walk API, instead
of directly accessing tbl and future_tbl
- Added rhashtable_walk_enter_from() into rhashtable to support O(1)
iteration continuations
- Link to v1: https://lore.kernel.org/r/20260205-rhash-v1-0-30dd6d63c462@meta.com
---
====================
Link: https://patch.msgid.link/20260605-rhash-v7-0-5b8e05f8630d@meta.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
